The invention relates to an antistatic molded article comprising a polyesteramide resin, particularly a molded article comprising a resin prepared by copolymerizing a cyclic amide and a cyclic ester and/or a linear ester, and further a molded article comprising a polyesteramide resin prepared by reacting a chemical compound having at least two hydroxyl groups, together with the above monomers.
A molded resin article provided with an antistatic property is widely used in electric appliances and electronic instruments. Especially, this is used in various kinds of parts used in production lines of semiconductor-related products, such as carrier pallets, housings, bearings, guides, and rollers.
To provide an antistatic property to a polymer matrix, for example, thermoplastic resins, the following methods have been employed: to add an electrically conductive filler such as graphite, carbon black, carbon fibers, metal oxides, metal powder, and metal fibers; to add or apply an antistatic agent to the surface, such as a surface-active agent; or to add an electrically conductive polymer.
It is rather easy to decrease a surface conductivity by blending in an electrically conductive filler. However, the filler must be added usually in an amount of as much as about 20 wt % of the molded article, so that homogeneous dispersion is difficult. Further, there is a problem of high costs. When an electrically conductive carbon filler is used, a molded article gets black and therefore coloration is limited, and sometimes its application field may be limited because of contamination with carbon powder. Further, it is difficult to steadily attain a required resistivity range of an order of from 109 to 1012xcexa9. If the resistivity is lower than this, in IC related parts, circuits in the IC may be damaged.
In the case where a surface-active agent is added to the polymerization system, the surface-active agent may inhibit the reaction or decompose at a high mold temperature; and even when the required resistivity is attained, the resistivity may change with time or a problem of ion extraction may arise, which problem is fatal in semiconductor production lines. In the case where a surface-active agent is applied on a surface of a molded article, there are problems that heat resistance is poor; the antistatic property degrades with time; and the surface-active agent adversely affects circuits in IC related parts.
The use of an electrically conductive polymer is better in that there is not the problem of ion extraction. However, the polymer is very expensive, and the molding temperature may be a limiting factor, like in the case of the use of a surface-active agent.
The object of the present invention is to provide an antistatic molded article having a desired surface resistivity without using a substantive amount of an electrically conductive additive, which article can be obtained easily and economically.
To solve the above problems, the present inventor has had an idea of attaining using a substantive amount of an electrically conductive antistatic property only by molecular skeleton structure without using a substantive amount of an electrically conductive additive, and has completed the present invention.
Thus the present invention is an antistatic molded article comprising a polyesteramide resin, characterized in that said molded article is prepared by copolymerizing (a) a cyclic amide and at least one ester selected from the group consisting of (b1) a cyclic ester and (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol, said molded article having a surface resistivity of less than 1013xcexa9.
Preferred embodiments of the above antistatic molded article comprising a polyesteramide resin are as follows:
the antistatic molded article comprising a polyesteramide resin, wherein the surface resistivity is in a range of from 109 to 1012xcexa9;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by ring-opening copolymerizing the cyclic amide (a) and the cyclic ester (b1) in a weight ratio of (a) to (b1) of from 100:3 to 100:44;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the cyclic ester (b1) in a weight ratio of (a) to (b1) of from 100:3 to 100: less than 10, wherein an electrically conductive material is further provided;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by ring-opening copolymerizing the cyclic amide (a) and the cyclic ester (b1) in a weight ratio of (a) to (b1) of from 100:10 to 100:34;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the linear ester (b2), or a mixture of the linear ester (b2) and the cyclic ester (b1) in a weight ratio of (a) to (b2) or (a) to the mixture of (b2) and (b1) of from 100:2 to 100:50;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the linear ester (b2) or a mixture of the linear ester (b2) and the cyclic ester (b1), in a weight ratio of (a) to (b2) or (a) to the mixture of (b2) and (b1) of from 100:2 to 100: less than 5, wherein an electrically conductive material is further provided;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the linear ester (b2) or the mixture of the cyclic ester (b1) and the linear ester (b2), in a weight ratio of (a) to (b2) or (a) to the mixture of (b2) and (b1) of from 100:5 to 100:45;
the antistatic molded article comprising a polyesteramide resin, having a tensile strength, measured according to ASTM D-638, of at least 40 MPa;
the antistatic molded article comprising a polyesteramide resin, wherein the linear ester (b2) is polycaprolactonediol;
the antistatic molded article comprising a polyesteramide resin, wherein the cyclic ester (b1) is xcex5-caprolactone; and
the antistatic molded article comprising a polyesteramide resin, wherein the cyclic amide (a) is xcex5-caprolactam.
Further, the present invention relates to a polyesteramide resin prepared by reacting 100 parts by weight of (a) a cyclic amide, 5 to 50 parts by weight of (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol, or 5 to 50 parts by weight of a mixture of at least 5 parts by weight of the linear ester (b2) and (b1) a cyclic ester, and (c) a chemical compound having a molecular weight of 200 or smaller and having at least 2 hydroxyl groups, wherein said resin has a number average molecular weight, reduced from polystyrene, of from 4,000 to 100,000.
Preferred embodiments of the above polyesteramide resin are as follows:
the polyesteramide resin, wherein said polyesteramide resin has the surface resistivity of from 106 to 109xcexa9;
the polyesteramide resin, wherein said polyesteramide resin has a volume resistivity of from 104 to 107 xcexa9.m.;
the polyesteramide resin, wherein the chemical compound (c) is used in such an amount that a molar ratio of the hydroxyl groups, defined by the following equation, is in a range of from 0.1 to 1.0, wherein the molar ratio of the hydroxyl groups=molar amount of the hydroxyl group of the chemical compound (c)/molar amount of the hydroxyl group of the linear ester (b2);
the polyesteramide resin, wherein the molar ratio of the hydroxyl groups is in the range of from 0.2 to 0.5;
the polyesteramide resin, wherein the chemical compound (c) has at least 3 hydroxyl groups;
the polyesteramide resin, wherein the chemical compound (c) is trimethylolethane, trimethylolpropane or a mixture of trimethylolethane and trimethylolpropane;
the polyesteramide resin, wherein the cyclic amide (a) is xcex5-caprolactam;
the polyesteramide resin, wherein the cyclic ester (b1) is xcex5-caprolactone;
the polyesteramide resin, wherein the linear ester (b2) is polycaprolactonediol; and
an antistatic molded article comprising the above mentioned polyesteramide resin.
Any one of the above-mentioned molded article is prepared preferably by a monomer casting method.
Further, the present invention is a method for preparing an antistatic polyesteramide resin by ring-opening copolymerizing (a) a cyclic amide and (b1) a cyclic ester in a weight ratio of from 100:3 to 100:44.
In the above method, it is preferred that the cyclic amide (a) and the cyclic ester (b1) are ring-opening copolymerized in a weight ratio of from 100:10 to 100:34.
Still further, the present invention is a method for preparing an antistatic polyesteramide resin by copolymerizing (a) a cyclic amide and (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol or a mixture of the linear ester (b2) and (b1) a cyclic ester, in a weight ratio of from 100:2 to 100:50.
In the above method, it is preferred that the cyclic amide (a) and the linear ester (b2) or the mixture of the linear ester (b2) and the cyclic ester (b1) are copolymerized in a weight ratio of from 100:5 to 100:45. It is also preferred that either the linear ester (b2) is polycaprolactonediol; that the cyclic ester (b1) is xcex5-caprolactone; and that the cyclic amide (a) is xcex5-caprolactam.
Further, the present invention is a method for preparing a polyesteramide resin by reacting 100 parts by weight of (a) a cyclic amide, 5 to 50 parts by weight of (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol, or 5 to 50 parts by weight of a mixture of (b2) at least 5 parts by weight of the linear ester and (b1) a cyclic ester, and (c) a chemical compound having a molecular weight of 200 or smaller and having at least 2 hydroxyl groups.
The preferred embodiments of the above method are as follows:
the method for preparing a polyesteramide resin, wherein the chemical compound (c) is reacted in such an amount that the molar ratio of the hydroxyl groups, defined by the following equation, is in the range of from 0.1 to 1.0, wherein the molar ratio of the hydroxyl groups=molar amount of the hydroxyl group of the chemical compound (c)/molar amount of the hydroxyl group of the linear ester (b2);
the method for preparing a polyesteramide resin, wherein the molar ratio of the hydroxyl group is in the range of from 0.2 to 0.5;
the method for preparing a polyesteramide resin, wherein the chemical compound (c) has at least 3 hydroxyl groups;
and the method for preparing a polyesteramide resin, wherein the chemical compound (c) is trimethylolethane, trimethylolpropane of a mixture of trimethylolethane and trimethylolpropane.
In any one of the above methods, it is preferred that either the cyclic amide (a) is xcex5-caprolactam; that the cyclic ester (b1) is xcex5-caprolactone; and that the linear ester (b2) is polycaprolactonediol.
It is preferred that a monomer casting method is used for the copolymerization in any one of the above-mentioned methods.
Further, the present invention is a method for making a polyesteramide resin antistatic, wherein the polyesteramide resin molded article is prepared by ring-opening copolymerizing (a) a cyclic amide and (b1) a cyclic ester, characterized in that the ratio of the cyclic amide (a) to the cyclic ester (b1) is set in a range of from 100:3 to 100:44.
In the above method, it is preferred that the ratio of the cyclic amide (a) to the cyclic ester (b1) is set in a range of from 100:10 to 100:34.
Still further, the present invention is a method for making a polyesteramide resin antistatic, wherein the polyesteramide resin is prepared by copolymerizing (a) a cyclic amide and (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol and polycarbonatepolyol or a mixture of the linear ester (b2) and (b1) a cyclic ester, characterized in that the weight ratio of the cyclic amide (a) to the linear ester (b2) or to the mixture of the cyclic ester (b1) and the linear ester (b2) is set in a range of from 100:2 to 100:50.
In the above method, it is preferred that the weight ratio of the cyclic amide (a) to the linear ester (b2) or the mixture of the cyclic ester (b1) and the linear ester (b2) is set in a range of from 100:5 to 100:45.
The present invention also relates to a method for making a polyesteramide resin antistatic, wherein the polyesteramide resin is prepared by copolymerizing (a) a cyclic amide and (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol or a mixture of the linear ester (b2) and (b1) a cyclic ester, characterized in that the weight ratio of the cyclic amide (a) to the linear ester (b2) is set in the range of from 100:5 to 100:50, or the weight ratio of the cyclic amide (a) to the mixture of the linear ester (b2) and the cyclic ester (b1) is set in the range of from 100:5 to 100:50, wherein the weight ratio of the linear ester (b2) to the cyclic amide (a) is at least 5:100, and (c) a chemical compound having a molecular weight of 200 or smaller and having at least 2 hydroxyl groups.
The preferred embodiments of the above method are as follows:
the method for making the polyesteramide resin antistatic, wherein the chemical compound (c) is added in such an amount that the molar ratio of the hydroxyl groups, defined by the following equation, is in the range of from 0.1 to 1.0, wherein the molar ratio of the hydroxyl groups=molar amount of the hydroxyl group of the chemical compound (c)/molar amount of the hydroxyl group of the linear ester (b2);
the method for making the polyesteramide resin antistatic, wherein the molar ratio of the hydroxyl groups is in the range of from 0.2 to 0.5;
the method for making the polyesteramide resin antistatic, wherein the chemical compound (c) has at least 3 hydroxyl groups; and
the method for making the polyesteramide resin antistatic, wherein the chemical compound (c) is trimethylolethane, trimethylolpropane or a mixture of trimethylolethane and trimethylolpropane.
In any one of the above methods for making a polyesteramide resin antistatic, it is preferred that either the cyclic amide (a) is xcex5-caprolactam; that the cyclic ester (b1) is xcex5-caprolactone; and that the linear ester (b2) is polycaprolactonediol.
It is preferred that a monomer casting method is used to prepare a polyesteramide resin in any one of the above-mentioned methods for making the polyesteramide resin antistatic.